Object segmentation has been of interest since the advent of 3D imaging technology such as MRI (magnetic resonance imaging) and CT (computed tomography). In medical imaging, segmentations of anatomic regions allow morphologic analysis of anatomy for the purpose of disease detection, diagnosis, progression monitoring, and treatment planning. For example, orbital fractures generally result from a force applied directly to the globe (eyeball) with disruption of the bony orbital architecture. This effectively distorts the orbital volume and dislocates the globe and surrounding structures to conform to the new orbital contour. Delineating the bony orbit from a CT scan of a human head provides additional information, such as volume and shape, to a surgeon when treating orbital fractures.
FIG. 1 is a CT scan of a human head with an axial slice through the orbits. The dotted line shows the boundary of an orbit. It is implicitly defined by the surrounding bone and there is no reliable functional boundary at the anterior opening or at the optic nerve canal. Label A represents the orbit region to be delineated. Labels B through F represent problem areas for segmentation methods B indicates thin nasal bones which are poorly represented by CT. Additionally, sinusitis (fluid in the sinuses) obfuscates this region. C indicates the anterior opening which has no bony boundary. Due to swelling of the soft tissue in this area for most trauma patients, it cannot be reliably used as a boundary. D and E indicate the orbit interior contains extraocular muscles and fat and often contains air, puss pockets, and bone fragments in trauma patients. Additionally, there can be large fractures in any of the orbital walls. F indicates the optic nerve canal which does not have a bony boundary.
Current methods for measuring orbital volume from CT scans include manually outlining the orbital contents slice-by-slice from an axial CT scan. This technique is tedious and typically requires over an hour. The interoperator variability and time required preclude routine clinical use of this manual method. A fast, automatic, repeatable and accurate method that obtains the quantitative morphological measurements of orbital volume can significantly aid in diagnosis and treatment of orbital injuries.
3D segmentation methods typically rely on a gradient boundary surrounding the region being segmented. However, orbits do not have a well-defined gradient boundary and the vast majority of the region's boundary is not defined functionally. This problem defining orbits extends to a wider variety of segmentation applications.
U.S. Pat. No. 8,194,964, commonly owned by the present assignee, dramatically advanced the state of the art by providing powerful technologies for identifying anatomic regions of a person delineated from image data. The present inventors have recognized that aspects of this technology can be adapted and extended for other medical and scanning image segmentation applications.